1. Technical Field
The present invention relates to tire building equipment and in particular to a tire building drum having increased bead holding capacity, increased sealing of the internal tire inflation chamber, and a drum more easily maintained and adaptable for different bladder configurations.
2. Background Information
Tire building drums have been used for many years in the manufacture of green tires. Many such drums consist of a pair of movable end drum sections, with or without a stationary central section, on which the various tire components or plies are laid in a layered relationship. After the plies are placed about the drum, a pair of bead ring assemblies are brought into position and retained about the ply ends by expandable bead locks. Next, inflatable turn-up bladders turn the edges of the plies at the drum ends over onto themselves to encase the bead ring assemblies within the carcass of the green tire. These tire building drums have a variety of constructions, certain of which are set forth in various prior art patents described later below.
One of the important features of a tire building drum is the ability to clamp the ply ends against the bead ring assemblies during inflation of the green tire and during inflation of the turn-up bladders when turning the ply ends upon themselves and around the bead ring assemblies. Sufficient strength must be applied to prevent the body ply ends from slipping during expansion of the tire in order to provide for a uniform high-quality green tire carcass.
The green tire carcass also must be inflated on the drum, which is generally accomplished by forming an internal tire inflation chamber on the inside of the drum which is in communication with the interior of the green tire. It is critical to maintain an efficient air seal for this tire inflation chamber to ensure that the correct pressure is exerted on the green tire carcass and maintained thereon during the turn-up operation on the ply ends. It is also desirable that when using a pair of turn-up bladders that they inflate generally simultaneously after the expansion of the spaced pair of bead lock assemblies.
The prior art and the features thereof, which applicant believes is of interest with respect to the present invention, is set forth in the following patents.
U.S. Pat. No. 3,237,199 discloses a tire building apparatus having a substantially T-shaped bead register segment of the general type of the present invention.
U.S. Pat. No. 3,645,826 discloses a tire building drum using an annular bladder support and clamp ring, which are secured to a carrier to which the bladders are secured. The bladder support has openings with air supply pipes for inflation of the bladders.
U.S. Pat. No. 4,226,656 discloses a tire building assembly wherein the turn-up bladder has clamping means to secure it to the drum, and the bead lock assembly is actuated by a pneumatic piston arrangement. Edges of the turn-up bladders are clamped by clamp rings, and compressed air is delivered into a cylinder which causes movement of a piston which moves struts that move the bead seating ring outwardly-into clamping engagement with the bead ring.
U.S. Pat. No. 4,239,579 discloses a tire building drum using a pneumatic piston arrangement to expand the bead seating segments. The turn-up bladder is supported by the interaction of a space ring, support ring, and a drum extension.
U.S. Pat. No. 4,244,770 discloses a tire building drum having both inboard and outboard dual bladder turn-up assemblies and radially expanding bead locks. The dual bladder turn-up assemblies are positioned at the exterior of the drum, and a pair of annular elastic bead locks are formed from rings. The annular rings have a T-shaped configuration which support side plates.
U.S. Pat. No. 4,290,472 discloses a tire building drum utilizing ply turn-up bladders and bead lock clamping members, together with bead lock clamp members which are positioned at the inner ends of a body portion of the drum segments. Straight links are utilized to join an inner leg to a piston which is actuated when air is introduced into cylinders to cause the pistons and link to move axially outward so that the bead lock clamping members retract.
U.S. Pat. No. 4,302,274 discloses a tire building drum having inner and outer annular bladders with embedded flanged inserts positioned in the bladder. An outer support ring and cylinder are radial supports for the bladder, and air supply tubes are attached to a branch connection for uniform delivery of inflating air to the bladder. O-rings are provided to form seals with the branch fitting.
U.S. Pat. No. 4,976,804 discloses a tire building drum utilizing bottom and top turn-up bladders. A bladder support cylinder has air passages which allows air to be delivered to the bladders at each end of the drum. Furthermore, links connect a hub portion and the end portions of the drum segments for expanding the end portions outwardly.
U.S. Pat. No. 5,223,074 discloses a bead locking apparatus for a tire building drum in which an elastic ring is fitted in an annular recess formed in the outer periphery of an annular arrangement of segments. A segment drive device moves the bead support segments radially outwardly. Another device is provided for radially expanding the elastic ring independent of the segments. The bead is first locked by the elastic ring, and then secondarily locked by the support segments.
U.S. Pat. No. 5,232,542 discloses a tire building drum having an axially sliding body having a plurality of tapered segments. The body is moved along the drum for expanding and contracting an outer segment for affecting the diameter of the drum.
Although the above patents disclose some of the individual features and modes of operation of the present invention, none of the patents, individually or when combined, show the particular arrangement of elements of the improved tire building drum of the present invention.